This is ThriveLeads opt-in plugin demo: ThriveBox which is triggered by clicking a link.
Click this link to trigger a ThriveBox. And the light box (popup window) will appear.
It can be one-step opt-in, multi-step or not an opt-in at all (e.g. a special offer or discount code etc).
Read my ThriveLeads review here.
Go to ThriveLeads website.